Increased intracranial pressure (ICP) is a serious complication in head injury and other neurologic conditions. Increased ICP compromises the cerebral circulation and can lead to permanent ischemic damage or death. Measurement of ICP forms the basis of rational therapy aimed at controlling its level. Such measurements are invasive and involve implanting transducers or catheters within-the cranium. A method for determining the ICP without having to implant measurement devices would be of considerable interest in the neurosurgical and neurological intensive care. It would be useful to have a non-invasive test and monitoring method to measure the ICP in a variety of conditions such as head injury, intracerebral hemorrhage, subarachnoid hemorrhage, pseudotumor cerebri, hydrocephalus and shunt obstruction, as well as in other conditions. The central theme of this proposal is to develop a method to estimate intracranial pressure (ICP) non-invasively. Transcranial Doppler (TCD) can be used to continuously record blood flow velocity from the intracranial vessels which then can be used in combination with arterial blood pressure (ABP) recording to measure the vascular tone and overall resistance in the cerebrovascular bed, which can be used to estimate intracranial pressure. We propose to utilize this information to establish the scientific principles to calculate intracranial pressure non-invasively from TCD and ABP measurements. We then propose to test this method for accuracy of continuous recording of ICP under ICU conditions.